A tuple with only one element must end with a comma. Python won't know it's a tuple without the comma. Probably not what you intended to do.

As far as the Python parser is concerned the parentheses are optional for non-empty tuples. According to the documentation: it is actually the comma which makes a tuple, not the parentheses. The parentheses are optional, except in the empty tuple case.

value = ()  # evaluates to empty tuple
values = 1,2  # evaluates to tuple with two elements
values = (1, 2)  # evaluates to tuple with two elements
values = (1)  # evaluates to int
values = (1,)  # evaluates to tuple with one element
values = 1, 2  # evaluates to tuple with two elements

By missing the comma in values = (1) expect to get a TypeError when the code later attempts to perform tuple operations on a variable that evaluated to int.